hwpmc_x86: Register interrupt handler using the dynamic NMI registrat…

…ion interface

Register the PCINT handler using the nmi_{register, remove}_handler
interfaces (introduced in D46421) in preparation for hwt(4)'s
Intel Processor Trace backend. No functional change intended.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D47989

sys/dev/hwpmc/hwpmc_x86.c

@@ -248,6 +248,7 @@ pmc_md_initialize(void)
 				continue;
 			md->pmd_classdep[i].pcd_caps &= ~PMC_CAP_INTERRUPT;
 		}
+	nmi_register_handler(md->pmd_intr);
 
 	return (md);
 }
@@ -257,6 +258,7 @@ pmc_md_finalize(struct pmc_mdep *md)
 {
 
 	lapic_disable_pcint();
+	nmi_remove_handler(md->pmd_intr);
 	if (cpu_vendor_id == CPU_VENDOR_AMD ||
 	    cpu_vendor_id == CPU_VENDOR_HYGON)
 		pmc_amd_finalize(md);